at this point why not use something like rabbitmq and not reinvent it in postgres.

Because it's trivially easy. The dequeue operation updates the last_lease time; the query makes sure you don't dequeue something that was recently leased. It's far, far easier than setting up a separate job queue, especially if you are already using an RDBMS.

Because then you're running and maintaining another service. Might make sense, but depends.